This invention relates to a coil material supply apparatus for supplying a coil material to an intermittent feed device of a mechanical press (pressing machine) in a pressing line.
With a high-speed pressing operation, the time used for intermittently feeding a coil material has become short, and the coil material is repeatedly fed and stopped in such a short time. As a result, the coil material vibrates by an exciting force exerted thereon, so that a wavy phenomenon called "fluttering" occurs. When such fluttering of the coil material occurs, not only an excessive burden or load is imposed on a feed device, but also the coil material is bent or damaged. To prevent this, it has been proposed to provide a buffer section called a "looper".
FIG. 2 shows a U-shaped looper, and that portion of a coil material 1 lying between an uncoiler 2 for unwinding the coil material 1 and an intermittent feed device 4 of a mechanical press 3 has a U-shaped buffer section. FIG. 3 shows an S-shaped looper, and that portion of a coil material 1 lying between an uncoiler 2 for unwinding the coil material 1 and an intermittent feed device 4 of a mechanical press 3 has an S-shaped buffer section.
With such conventional U-shaped looper or S-shaped looper, the fluttering of the coil material is reduced as compared with the case where no buffer section is provided; however, the fluttering still occurs when the operation is carried out at high speed, and therefore the increase of the operation speed has been limited, so that the ability of the press could not fully be utilized. Moreover, the looper itself has no drive source, and therefore the feed of the coil material depends on a pulling force from the intermittent device, or a pushing force from a leveler for flatting the coil material unwound from the uncoiler. Accordingly, the resistance is increased because of such pulling force and pushing force, so that the ability of the intermittent feed device or the leveler to supply the coil material has been lowered. A further problem is that since the length of the buffer section needs to be relatively large, the length of the pressing line has been increased.